Mousse alternative (3)
I believe the answer is:
gel
'mousse alternative' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gel that I've seen before include "Capital preparation" , "well-spoken deb?" , "Come together, take shape (colloq.)" , "It may be applied to locks" , "stiffen" .)